AIR CONDITIONER INCLUDING INDOOR UNIT

Abstract

An indoor unit for an air conditioner including a centrifugal fan. The centrifugal fan includes a main plate connectable to a rotation shaft of a motor, a plurality of blades, with one respective end to be bonded to the main plate and arrangeable at equal intervals from each other along a circumferential direction, a shroud, to be bonded to another respective end of the plurality of blades, to face the main plate, and a bell mouth arrangeable inside the shroud. An annular member arrangeable on an outer circumferential portion of the bell mouth with an inlet portion at the gap between the shroud and the bell mouth. The annular member including an annular flat plate portion spaced apart from and face the inlet portion, and a protrusion formed on an outer circumferential portion of a surface of the annular flat plate portion facing the shroud and being curved.

Description

TECHNICAL FIELD

The present disclosure relates to an indoor unit for an air conditioner, the indoor unit having a centrifugal fan.

BACKGROUND ART

An indoor unit for an air conditioner sucks in indoor air through an intake port. The sucked-in air undergoes heat exchange with a heat exchanger, and then is discharged back indoors through an exhaust port. The indoor unit for an air conditioner includes a centrifugal fan that sucks in air from the room through the intake port, and discharges the air into the room through the exhaust port. A portion of air blowing out from an outlet of the centrifugal fan and then heading toward the exhaust port may flow into an inlet of the centrifugal fan through a gap between a shroud and a bell mouth. The flow of the air reintroduced from the outlet of the centrifugal fan into the inlet is referred to as a leakage flow (a recirculating flow). The leakage flow (recirculating flow) may cause poor blowing performance and noise in the centrifugal fan.

Japanese Patent Laid-Open Publication No. 2010-133297 discloses a technique for reducing the amount of leakage flow by installing, on the outer circumference of an air outlet of a bell mouth, a sealing wall having a U-shaped cross-section that covers a suction-side end of a shroud to lengthen a leakage flow path and increase an air flow resistance.

DISCLOSURE

Technical Solution

An indoor unit for an air conditioner according to an aspect of the present disclosure includes a centrifugal fan to suck in air through an air intake port and discharge the air through an air discharge port, and a heat exchanger to exchange heat with an air flow generated by the centrifugal fan. The centrifugal fan includes a main plate connectable to a rotation shaft of a motor. A plurality of blades, with one respective end to be bonded to the main plate so that while the one respective end of the plurality of blades is bonded to the main plate, the plurality of blades are arranged at equal intervals from each other in a circumferential direction. A shroud to be bonded to another respective end of the plurality of blades to face the main plate. The shroud having an annular shape with an opening at the center thereof. The bell mouth is arrangeable inside the shroud. A gap is formed between the shroud and the bell mouth to allow a recirculating flow of the air sucked through the air intake port and passed through the opening of the shroud to pass through the gap. The bell mouth has an inner diameter that gradually increases toward the upstream side of the recirculating flow. An annular member is provided on an outer circumferential portion of the bell mouth. The annular member is arrangeable to be spaced apart from an inlet portion at the gap between the shroud and the bell mouth on the upstream side of the recirculating flow along a rotation axis direction of the shroud. The annular member includes an annular flat plate portion spaced apart from an upstream end of the inlet portion, and facing the upstream end of the inlet portion of the shroud, and a protrusion formed on an outer circumferential portion of a surface of the annular flat plate portion facing the shroud, the protrusion having an outer surface that is curved.

An indoor unit for an air conditioner according to an aspect of the present disclosure includes a centrifugal fan to suck in air through an air intake port and discharge the air through an air discharge port, and a heat exchanger to exchange heat with an air flow generated by the centrifugal fan. The centrifugal fan includes a main plate connectable to a rotation shaft of a motor. A plurality of blades, with one respective end to be bonded to the main plate so that while the one respective end of the plurality of blades is bonded to the main plate, the plurality of blades are arranged at equal intervals from each other in a circumferential direction. A shroud to be bonded to another respective end of the plurality of blades to face the main plate. The bell mouth is arrangeable inside the shroud and spaced apart from the shroud to allow air flow. The bell mouth has an inner diameter that gradually increases toward an upstream side of the air flow. An annular member is provided on an outer circumferential portion of the bell mouth. The annular member arrangeable to be spaced apart from an inlet portion at the gap between the shroud and the bell mouth on an upstream side of the shroud along a rotation axis direction of the shroud. A communication flow path to allow flow of air along the rotation axis of the shroud and is formed between the annular member and the bell mouth.

According to the above configuration, it is possible to reduce recirculating flow, prevent damage to the shroud or the bell mouth due to contact, and reduce windage losses.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of an indoor unit for an air conditioner according to an embodiment of the present disclosure.

FIG. 2 is a partially enlarged cross-sectional view illustrating a structure for reducing a recirculating flow, according to an embodiment.

FIG. 3A is a schematic diagram defining distances between an upstream end of a shroud and a plurality of portions on a bell mouth and an annular member.

FIG. 3B is a graph showing an example of distances between an upstream end of a shroud and a plurality of portions on a bell mouth and an annular member.

FIG. 3C is a graph showing an example of fluid frictional losses at a plurality of portions on a bell mouth and an annular member.

FIG. 4 is a partially enlarged cross-sectional view illustrating a structure for reducing a recirculating flow, according to an embodiment.

FIG. 5 is a partially enlarged cross-sectional view illustrating a structure for reducing a recirculating flow, according to an embodiment.

FIG. 6 is a partially enlarged cross-sectional view illustrating a structure for reducing a recirculating flow, according to an embodiment.

MODE FOR INVENTION

Although the terms used herein are selected from among common terms that are currently widely used in consideration of their functions in the disclosure, the terms may be different according to an intention of one of ordinary skill in the art, a precedent, or the advent of new technology. Also, in particular cases, the terms are discretionally selected by the applicant of the present disclosure, in which case, the meaning of those terms will be described in detail in the corresponding part of the detailed description. Therefore, the terms used herein are not merely designations of the terms, but the terms are defined based on the meaning of the terms and content throughout the present disclosure. Throughout the present specification, when a part “includes” a component, it means that the part may additionally include other components rather than excluding other components as long as there is no particular opposing recitation.

Hereinafter, embodiments will be described with reference to the accompanying drawings in such a manner that the embodiments may be easily carried out by one of skill in the art. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to an embodiment set forth herein. In order to clearly describe the present disclosure, portions that are not relevant to the description of the present disclosure are omitted, and similar reference numerals are assigned to similar elements throughout the present specification. Hereinafter, a washing machine according to embodiments of the present disclosure will be described with reference to the drawings. Hereinafter, a centrifugal fan and an indoor unit for an air conditioner using the centrifugal fan according to embodiments of the present disclosure will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of an indoor unit for an air conditioner according to an embodiment of the present disclosure. Referring to FIG. 1, an indoor unit 100 for an air conditioner according to an embodiment of the present disclosure is of a ceiling-mounted type. An air intake port H1 and an air discharge port H2 are formed on a lower surface of the indoor unit 100 for an air conditioner. In the present embodiment, at least one air intake port H1 is formed in a central portion of the lower surface, and at least one, for example, four air discharge ports H2 are formed to surround the air intake port H1. In the present embodiment, the four air discharge ports H2 are formed to correspond to the four sides of a quadrangle in a plan view. However, shapes, numbers, and an arrangement of air intake ports H1 and air discharge ports H2 are not limited thereto. For example, one or more air discharge ports H2 may have an annular shape surrounding the air intake port H1.

The indoor unit 100 for an air conditioner may include a centrifugal fan 2 and a heat exchanger 3. The centrifugal fan 2 and the heat exchanger 3 are accommodated in the indoor unit 100 for an air conditioner. The centrifugal fan 2 sucks in air into the indoor unit 100 for an air conditioner through the air intake port H1, and blows air out of the indoor unit 100 for an air conditioner through the air discharge port H2. An air flow generated by the centrifugal fan 2 is brought into contact with the heat exchanger 3 to undergo heat exchange. The heat exchanger 3 may be arranged to surround the centrifugal fan 2. The air sucked in by the centrifugal fan 2 through the air intake port H1 undergoes heat exchange by the heat exchanger 3, and then is blown out indoors through the air discharge port H2.

As illustrated in FIG. 1, the centrifugal fan 2 according to an embodiment may include a main plate 21, a plurality of blades 22, a shroud 23, and a bell mouth 24.

The main plate 21 includes a boss portion 21a. A rotation shaft 41 of a motor 4 is connected to the center of the boss portion 21a. By this connection, the main plate 21 is connected to the rotation shaft 41 of the motor 4. The shape of the main plate 21 in a plan view may be a disk shape. A protrusion 21b is formed in a central portion of the main plate 21. For example, the protrusion 21b protrudes from the downstream side toward the upstream side with respect to the flow direction of the air flow to be described below.

One end 22a of the plurality of blades 22 may be bonded to one surface 21-1 of the main plate 21 on which the protrusion 21b is formed. The plurality of blades 22 may be arranged at equal intervals from each other in the circumferential direction (i.e., the direction of rotation). The plurality of blades 22 may be formed from an outer circumferential surface 21b-1 of the protrusion 21b formed in the central portion of the main plate 21, to an outer circumference 21c of the main plate 21. A detailed configuration of the blade 22 will be described below.

The shroud 23 is located to face the main plate 21. The shroud 23 is bonded to one end 22b of the plurality of blades 22, has an annular shape, and has an opening 23-1 at the center thereof. Air is sucked in through the opening 23-1 at the center of the shroud 23. Air is blown out through an opening 23-2 formed between the shroud 23 and the main plate 21.

The bell mouth 24 is located on the upstream side in the direction of the rotation axis with respect to the shroud 23. In other words, the bell mouth 24 is located on the upstream side of the shroud 23 with respect to the direction of air flow. A downstream end 24a (see FIG. 2) of the bell mouth 24 is located inside the shroud 23. The bell mouth 24 may have an inner diameter that gradually increases from the downstream end 24a to the upstream side. A gap 28 is provided between the shroud 23 and the bell mouth 24 such that the shroud 23 does not interfere with the bell mouth 24 while the centrifugal fan 2 is rotating.

Part RF of air blowing out from an outlet of the centrifugal fan 2, for example, the opening 23-2, is directed toward the gap 28 between the shroud 23 and the bell mouth 24, and part RF2 (recirculating flow) of the part RF may pass through the gap 28 between the shroud 23 and the bell mouth 24 and then flow into the centrifugal fan 2 (see FIG. 1). The centrifugal fan 2 of the present disclosure has a structure for reducing the recirculating flow RF2. FIG. 2 is a partially enlarged cross-sectional view illustrating a structure for reducing the recirculating flow RF2, according to an embodiment. Referring to FIGS. 1 and 2, the centrifugal fan 2 includes an annular member (recirculating flow reduction member) 25. In an embodiment, the annular member 25 may be installed in an outer circumferential portion 24-1 of the bell mouth 24. The annular member 25 is located with a gap from an upstream end 23a (here, a lower end) of an inlet portion (the opening 23-1) of the shroud 23, on the upstream side (here, in the downward direction) in the direction of the rotation axis.

The annular member 25 may include an annular flat plate portion (first portion) 251 and a protrusion (second portion) 252 protruding from the annular flat plate portion 251 toward the shroud 23. The annular flat plate portion 251 may be supported by the bell mouth 24. The annular flat plate portion 251 may extend outward in the radial direction from the outer circumferential portion 24-1 of the bell mouth 24. The annular flat plate portion 251 is spaced upstream from the upstream end 23a of the inlet portion of the shroud 23 to face the upstream end 23a of the inlet portion of the shroud 23 with a gap therebetween. The protrusion 252 may be formed on an outer circumferential portion of a surface 251a of the annular flat plate portion 251 facing the shroud 23. The protrusion 252 is located at a farther outward position in the radial direction than the inlet portion of the shroud 23. In other words, the protrusion 252 is located at a farther outward position in the radial direction than the upstream end 23a of the inlet portion of the shroud 23. The outer surface of the protrusion 252 may be a smooth (soft) curved surface. For example, the cross-sectional shape of the outer surface of the protrusion 252 may be a partially circular shape or a beading shape. The upper end (downstream end) of the protrusion 252 is located further upstream (here, at a lower portion) in the direction of the rotation axis than the upstream end 23a of the inlet portion of the shroud 23. As illustrated in FIG. 2, the annular flat plate portion 251 has a closest portion 25x that is closest to the upstream end 23a of the inlet portion of the shroud 23. In the present embodiment, the closest portion 25x is a portion facing the upstream end 23a of the shroud 23 in the direction of the rotation axis. The protrusion 252 is spaced further apart from the upstream end 23a of the inlet portion of the shroud 23 than the closest portion 25x. When the shortest distance between the upstream end 23a of the inlet portion of the shroud 23 and the annular flat plate portion 251, for example, the distance between the upstream end 23a of the inlet portion of the shroud 23 and the closest portion 25x, is L1, and the distance (shortest distance) between the upstream end 23a of the inlet portion of the shroud 23 and the protrusion 252 is L2, L1<L2.

Referring to FIG. 2, the part RF1 of the air RF heading toward the gap 28 between the shroud 23 and the bell mouth 24 is discharged from the indoor unit 100 for an air conditioner through the heat exchanger 3, and the recirculating flow RF2 may flow toward the gap 28 between the shroud 23 and the bell mouth 24. According to the present embodiment, by providing the annular member 25, the part RF2 of the recirculating flow RF may be prevented from flowing into the gap 6 between the shroud 23 and the bell mouth 24. In addition, because the outer surface of the protrusion 252 is a smooth (soft) curved surface, the flow path through which the recirculating flow RF2 flows has an approximately S-shape, and thus, the recirculating flow RF2 flows in the approximately S-shape. As a result, as illustrated in FIG. 2, the amount of recirculating flow RF2 may be reduced. In addition, the recirculating flow RF2 flowing into the gap 28 between the shroud 23 and the bell mouth 24 flows into the centrifugal fan 2 along the outer circumferential surface 24-1 of the bell mouth 24 in front of the downstream end 24a of the bell mouth 24. At this time, the flow direction of the recirculating flow RF2 and the flow direction of an air flow 27 flowing into the centrifugal fan 2 along an inner circumferential surface 24-2 of the bell mouth 24 do not intersect each other near the downstream end 24a of the bell mouth 24, and thus, the recirculating flow RF2 and the air flow 27 may naturally join each other. Because the recirculating flow RF2 flows smoothly into the centrifugal fan 2, turbulence of an air flow in a flow path through which the recirculating flow RF2 flows and an air flow inside the centrifugal fan 2 may be suppressed and noise may be reduced. In addition, because the protrusion 252 is further away from the upstream end 23a of the shroud 23 than the closest portion 25x of the annular flat plate portion 251, fluid frictional losses may be suppressed when the recirculating flow RF2 flows into the gap 28, and the flow shape of the recirculating flow RF2 flowing into the inlet portion of the shroud 23 may be approximately S-shaped.

FIG. 3A is a schematic diagram defining distances between the upstream end 23a of the shroud 23 and a plurality of portions on the bell mouth 24 and the annular member 25. FIG. 3B is a graph showing an example of distances between the upstream end 23a of the shroud 23 and a plurality of portions on the bell mouth 24 and the annular member 25. FIG. 3C is a graph showing an example of fluid frictional losses at a plurality of portions on the bell mouth 24 and the annular member 25. Referring to FIGS. 3A, 3B, and 3C, according to an embodiment of the present disclosure, it may be seen that fluid frictional losses and unnecessary increases in torque at portions other than the closest portion 25x of the annular member 25 are suppressed.

According to the indoor unit 100 for an air conditioner according to an embodiment of the present disclosure, in the outer circumferential portion 24-1 of the bell mouth 24, the annular member 25 is provided with a gap on the upstream side in the direction of the rotation axis from the inlet portion of the shroud 23, and thus, the amount of air reintroduced into the centrifugal fan 2 through the gap 28 between the shroud 23 and the bell mouth 24 among the air discharged by the centrifugal fan 2, that is, the amount of the recirculating flow RF2, may be reduced. In addition, windage losses of the centrifugal fan 2 may be reduced. In addition, because the bell mouth 24 and the annular member 25 are spaced apart from the end 23a of the shroud 23, damage to the shroud 23 and/or the bell mouth 24 due to contact between the bell mouth 24 and the annular member 25, and the end 23a of the shroud 23 during transportation of the centrifugal fan 2, transportation of the indoor unit 100 for an air conditioner, and an operation of the centrifugal fan 2 may be reduced or prevented.

According to a related-art structure in which a sealing wall having a U-shaped cross section covering a suction-side end of a shroud is installed on an outer circumference of an air outlet of a bell mouth, the sealing wall forms a U-shaped structure that covers the suction-side end of the shroud, and thus, there is a risk that the shroud and/or the bell mouth may be damaged due to mutual contact interference due to vibration during transportation or an operation of a centrifugal fan. In addition, because the area of a portion where the sealing wall and the shroud are located close to each other, that is, the opposing area, is large, a fluid frictional loss due to viscosity near a flow path surface and a windage loss may increase, and thus, the blowing performance of the centrifugal fan may deteriorate.

According to the centrifugal fan 2 and the indoor unit 100 for an air conditioner according to an embodiment of the present disclosure, the annular member 25 includes the annular flat plate portion 251 which is installed to be spaced apart from and face the upstream end 23a of the inlet portion of the shroud 23, and the protrusion 252 which is formed on an outer circumferential portion of the surface 251 of the annular flat plate portion 251 facing the shroud 23 and has a smooth curved outer surface, and thus, the recirculating flow RF2 flows along the protrusion 252 and then along the annular flat plate portion 251. That is, the recirculating flow RF2 flows in an approximately S-shape, the length of the flow path of the recirculating flow RF2 increases, and thus, the flow resistance increases. As a result, the amount of recirculating flow RF2 may be reduced. In addition, because the annular member 25 includes the annular flat plate portion 251 and the protrusion 252, damage to the shroud 23 or the bell mouth 24 due to interference may be prevented. In addition, because an opposing surface between the annular member 25 and the shroud 23 may be relatively small, fluid frictional losses may be reduced, and thus, windage losses may be reduced. In addition, because the outer surface of the protrusion 252 is a smooth curved surface, noise may be reduced by suppressing turbulence due to an edge of the protrusion 252.

Embodiments of the centrifugal fan 2 and the indoor unit 100 for an air conditioner employing the same according to the present disclosure are not limited to the above-described embodiment.

For example, FIG. 4 is a partially enlarged cross-sectional view illustrating a structure for reducing a recirculating flow, according to an embodiment. Referring to FIG. 4, a communication flow path 26 for communication in the direction of the rotation axis (here, the vertical direction) may be formed between the annular member 25 and the bell mouth 24.

The communication flow path 26 may include a reduced portion 261 having a flow path cross-sectional area that gradually decreases from the inlet side (upstream side), and an enlarged portion 262 having a flow path cross-sectional area that gradually increases from the outlet side (downstream side) of the reduced portion 261. The communication flow path 26 may function as an orifice. While the flow velocity of an air flow RF3 flowing along the communication flow path 26 increases, the air flow RF3 flows toward the inlet portion of the shroud 23. By increasing the flow velocity of the air flow RF3 flowing through the communication flow path 26, it is possible to suppress the recirculating flow RF2 from heading toward the inner circumference of the centrifugal fan 2 when the recirculating flow RF2 flows into the centrifugal fan 2.

The communication flow path 26 is formed by and between the annular member 25, for example, an inner circumferential surface 251b of the annular flat plate portion 251, and the outer circumferential surface 24-1 of the bell mouth 24. Through this configuration, the air flow RF3 flowing through the communication flow path 26 flows along the outer circumferential surface 24-1 of the bell mouth 24. In addition, the width of the communication flow path 26 is less than the gap 28 between the shroud 23 and the bell mouth 24. Accordingly, the air flow RF3 flowing out of the communication flow path 26 may be easily formed near the outlet of the flow path of the recirculating flow RF2 and on the inner circumferential side relative to the recirculating flow RF2, without increasing the amount of the air flow RF3, that is, the amount of leakage flow.

The effect of the annular member 25 including the communication flow path 26 illustrated in FIG. 4 may be confirmed from a simulation result. For example, a simulation result of an air flow when the annular member 25 illustrated in FIG. 4 is applied may be compared with a simulation result of an air flow when the annular member 25 illustrated in FIG. 4 is not applied. It may be confirmed that, when the annular member 25 is not provided, the velocity of the recirculating flow (leakage flow) RF2 is high, and the recirculating flow RF2 flows toward the inner circumference of the centrifugal fan 2. It may be confirmed that, when the annular member 25 is provided, the velocity of the recirculating flow RF2 is reduced compared to the case without the annular member 25, and thus, the main stream of the recirculating flow RF2 easily flows toward the outer circumference of the centrifugal fan 2. That is, by providing the annular member 25, the main stream of the recirculating flow RF2 may be caused to flow in the outer circumferential direction in which the work of the blades 22 is large.

FIG. 5 is a partially enlarged cross-sectional view illustrating a structure for reducing a recirculating flow, according to an embodiment. Referring to FIG. 5, a front end portion 231 including the upstream end 23a of the inlet portion of the shroud 23 is formed into a smooth (soft) curved surface, and thereby, when the recirculating flow RF2 flows into the inlet portion of the shroud 23, the recirculating flow RF2 may be suppressed from being turbulence. For example, the cross-sectional shape of the front end portion 231 including the upstream end 23a of the inlet portion of the shroud 23 may be a partially circular shape or a beading shape.

FIG. 6 is a partially enlarged cross-sectional view illustrating a structure for reducing a recirculating flow, according to an embodiment. Referring to FIG. 6, the bell mouth 24 and the annular member 25 may be molded as one body. By molding the bell mouth 24 and the annular member 25 as one body, mechanical strength may be secured through a connection portion (not shown) connecting the bell mouth 24 to the annular member 25.

The communication flow path 26 for communication in the direction of the rotation axis is formed between the annular member 25 and the bell mouth 24. The communication flow path 26 is configured by using the inner circumferential surface of the annular member 25 and the outer circumferential surface 24-1 of the bell mouth 24. In detail, a flow path-forming wall portion 253 spaced apart from the outer circumferential surface 24-1 of the bell mouth 24 may be formed on an inner circumferential edge of the annular member 25. By appropriately determining the length of the flow path-forming wall portion 253, the communication flow path 26 may be set to have a desired flow path length. By setting the flow path length of the communication flow path 26 in this manner, the flow rate of the air flow RF3 flowing along the outer circumferential surface 24-1 of the bell mouth 24 may be easily adjusted.

In addition, the flow path cross-sectional area of the communication flow path 26 of FIG. 6 gradually increases from the inlet side toward the outlet side. This shape prevents undercut shapes from occurring in a mold during injection molding using the mold. Thus, a member into which the bell mouth 24 and the annular member 25 are integrated has a shape that is easy to manufacture through injection molding. In addition, because the width of the communication flow path 26 is less than the gap 28 between the shroud 23 and the bell mouth 24, the air flow RF3 flowing out of the communication flow path 26 may be easily formed near the outlet of the flow path of the recirculating flow RF2 and on the inner circumferential side relative to the recirculating flow RF2, without increasing the amount of the air flow RF3, that is, the amount of leakage flow.

The present disclosure is to reduce recirculating flow in a centrifugal fan of an indoor unit for an air conditioner, and prevent damage to a shroud or a bell mouth due to contact. In addition, the present disclosure is to reduce wind losses in the centrifugal fan of the indoor unit for an air conditioner.

An indoor unit for an air conditioner according to an aspect of the present disclosure includes: a centrifugal fan to suck in air through an air intake port and discharge the air through an air discharge port; and a heat exchanger to exchange heat with an air flow generated by the centrifugal fan, wherein the centrifugal fan includes: a main plate to which a rotation shaft of a motor is connected; a plurality of blades bonded to the main plate and arranged at equal intervals from each other in a circumferential direction; a shroud having an annular shape with an opening at a center thereof, the shroud being bonded to the plurality of blades, to face the main plate; a bell mouth located inside the shroud and having a gap from the shroud to allow a recirculating flow to pass through the gap, an inner diameter of the bell mouth gradually increasing toward an upstream side; and an annular member located at an outer circumferential portion of the bell mouth to be spaced apart from an inlet portion of the shroud on an upstream side in a rotation axis direction from the inlet portion of the shroud, and the annular member includes: an annular flat plate portion spaced apart from an upstream end of the inlet portion of the shroud, and facing the upstream end of the inlet portion of the shroud; and a protrusion formed on an outer circumferential portion of a surface of the annular flat plate portion facing the shroud, the protrusion having a smooth curved outer surface.

According to the centrifugal fan configured as described above, by providing the annular member with the gap from the inlet portion of the shroud, it is possible to reduce a recirculating flow, prevent damage to the shroud or the bell mouth due to contact, and reduce wind losses.

The recirculating flow flows along the protrusion and then along the annular flat plate portion, that is, flows in an approximately S shape, and thus, the length of the recirculating flow path increases and the flow resistance increases. As a result, the recirculating flow may be reduced. In addition, because the annular member includes the annular flat plate portion and the protrusion, damage to the shroud or the bell mouth due to contact may be prevented, and windage losses may be reduced by reducing fluid frictional losses between the annular member and the shroud. In addition, because the outer surface of the protrusion is a smooth curved surface, generation of turbulence caused by an edge of the protrusion may be suppressed, and thus generation of noise may be suppressed.

According to the present disclosure, rather than covering the inlet portion of the shroud to physically block it, by providing the gap between the shroud and the annular member, and forming an outer circumferential end of the annular member into a protrusion considering the flow of recirculating flow, it is possible to cause a recirculating flow to flow in an approximately S-shape, and achieve both a reduction in the flow rate of the recirculating flow and suppression of the occurrence of turbulence.

In a specific embodiment for forming the outer surface of the protrusion into a smooth curved surface, the cross-sectional shape of the outer surface of the protrusion may be partially circular.

In an embodiment for causing the recirculating flow flowing into the inlet portion of the shroud to flow in an approximately S-shape, the protrusion may be located at a farther outward position in the radial direction than the inlet portion of the shroud.

In an embodiment for suppressing fluid frictional losses and causing the recirculating flow flowing into the inlet portion of the shroud to flow in an approximately S-shape, the protrusion may be positioned further spaced apart from the upstream end of the inlet portion of the shroud than the closest portion of the annular flat plate portion that is closest to the upstream end of the inlet portion of the shroud.

A communication flow path for communication in the direction of the rotation axis may be formed between the annular member and the bell mouth. The communication flow path may form an air flow that flows along the outer circumferential surface of the bell mouth, and the air flow may cause the recirculating flow to flow along the inner circumferential surface of the shroud. As a result, turbulence caused by flow separation may be suppressed, and blowing noise may be reduced while improving the blowing performance.

The communication flow path may have an enlarged portion having a flow path cross-sectional area that gradually increases from the inlet side toward the outlet side. The communication flow path may have a reduced portion having a flow path cross-sectional area that gradually decreases, on the inlet side of the enlarged portion. The communication flow path may be formed between the inner circumferential surface of the annular flat plate portion and the outer circumferential surface of the bell mouth. The width of the communication flow path may be less than the gap between the shroud and the bell mouth.

An indoor unit for an air conditioner according to an aspect of the present disclosure includes: a centrifugal fan to suck in air through an air intake port and discharge the air through an air discharge port; and a heat exchanger to exchange heat with an air flow generated by the centrifugal fan, wherein the centrifugal fan includes: a main plate to which a rotation shaft of a motor is connected; a plurality of blades bonded to the main plate and arranged at equal intervals from each other in a circumferential direction; a shroud having an annular shape with an opening at a center thereof, the shroud being bonded to the plurality of blades, to face the main plate; a bell mouth installed inside the shroud and having an inner diameter that gradually increases toward an upstream side; and an annular member located at an outer circumferential portion of the bell mouth with a gap from an inlet portion of the shroud on an upstream side in a rotation axis direction from the inlet portion of the shroud, and a communication flow path for communication in the rotation axis direction is formed between the annular member and the bell mouth.

According to the above configuration, it is possible to reduce recirculating flow by using the annular member, prevent damage to the shroud or the bell mouth due to contact, and reduce windage losses. In addition, by forming the communication flow path, an air flow flowing along the outer circumferential surface of the bell mouth may be formed, and the air flow may cause the recirculating flow to flow along the inner circumferential surface of the shroud. As a result, turbulence caused by flow separation may be suppressed, and blowing noise may be reduced while improving the blowing performance.

In a specific embodiment of the communication flow path, the communication flow path may have an enlarged portion having a flow path cross-sectional area that gradually increases from the inlet side toward the outlet side. In addition, the communication flow path may have a reduced portion having a flow path cross-sectional area that gradually decreases, on the inlet side of the enlarged portion.

Through this configuration, the communication flow path may function as an orifice to increase the flow velocity of an air flow flowing through the communication flow path and cause the air flow to flow into the inlet portion of the shroud. In addition, by increasing the flow velocity of the air flow flowing through the communication flow path, it is possible to suppress the recirculating flow flowing into the centrifugal fan from heading toward the inner circumference.

In an embodiment, the communication flow path may be formed between the annular member and the outer circumferential surface of the bell mouth. Accordingly, a centrifugal fan having a simple structure with a communication flow path may be implemented.

In an embodiment, the width of the communication flow path may be less than a gap formed between the shroud and the bell mouth such that a recirculating flow passes through the gap. Accordingly, it is possible to cause the recirculating flow to efficiently flow along the inner circumferential surface of the shroud. In addition, an air flow flowing out of the communication flow path may be easily formed on the inner circumferential side of the recirculating flow near an outlet of the flow path of the recirculating flow without increasing the amount of leakage flow. In an embodiment, the communication flow path may have an enlarged portion having a flow path cross-sectional area that gradually increases from the inlet side toward the outlet side, and a reduced portion having a flow path cross-sectional area that gradually decreases, on the inlet side of the enlarged portion.

In addition, the indoor unit for an air conditioner using a centrifugal fan is described in the above embodiments, but the centrifugal fan of the present disclosure may also be used for other blowers.

In addition, it is needless to mention that the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

Claims

1. An air conditioner including an indoor unit, the indoor unit comprising: a centrifugal fan to suck in air through an air intake port and discharge the air through an air discharge port; anda heat exchanger to exchange heat with an air flow generated by the centrifugal fan,wherein the centrifugal fan comprises: a main plate connectable to a rotation shaft of a motor;a plurality of blades, with one respective end to be bonded to the main plate, so that while the one respective end of the plurality of blades is bonded to the main plate, the plurality of blades are arranged at equal intervals from each other along a circumferential direction;a shroud, having an annular shape with an opening at a center thereof, to be bonded to another respective end of the plurality of blades, the shroud to face the main plate;a bell mouth arrangeable inside the shroud to have a gap from the shroud to allow a recirculating flow of the air sucked through the air intake port and passed through the opening of the shroud to pass through the gap, the bell mouth having an inner diameter gradually increasing toward an upstream side of the recirculating flow; andan annular member arrangeable at an outer circumferential portion of the bell mouth to be spaced apart from an inlet portion at the gap between the shroud and the bell mouth on the upstream side of the recirculating flow along a rotation axis direction of the shroud, andthe annular member comprises: an annular flat plate portion spaced apart from an upstream end of the inlet portion and facing the upstream end of the inlet portion; anda protrusion formed on an outer circumferential portion of a surface of the annular flat plate portion facing the shroud, the protrusion having an outer surface that is curved.

2. The air conditioner of claim 1, wherein a cross-sectional shape of the outer surface of the protrusion is partially circular.

3. The air conditioner of claim 1, wherein the protrusion is farther than the inlet portion along a radial direction of the shroud.

4. The air conditioner of claim 1, wherein the annular flat plate portion has a portion closest to the upstream end of the inlet portion, and the protrusion is further spaced apart from the upstream end of the inlet portion than the portion of the annular flat plate portion closest to the upstream end of the inlet portion.

5. The air conditioner of claim 1, wherein a communication flow path for air flow along the rotation axis direction of the shroud is formed between the annular member and the bell mouth.

6. The air conditioner of claim 5, wherein the communication flow path has an enlarged portion having a cross-sectional area that gradually increases from an inlet side toward an outlet side.

7. The air conditioner of claim 6, wherein the communication flow path has a reduced portion, on the inlet side of the enlarged portion, having a flow path cross-sectional area that gradually decreases.

8. The air conditioner of claim 5, wherein the communication flow path is formed between an inner circumferential surface of the annular flat plate portion and an outer circumferential surface of the bell mouth.

9. The air conditioner of claim 5, wherein a width of the communication flow path is less than the gap between the shroud and the bell mouth.

10. An air conditioner including an indoor unit, the indoor unit comprising: a centrifugal fan to suck in air through an air intake port and discharge the air through an air discharge port; anda heat exchanger to exchange heat with an air flow generated by the centrifugal fan,wherein the centrifugal fan comprises: a main plate connectable to a rotation shaft of a motor;a plurality of blades, with one respective end to be bonded to the main plate, so that while the one respective end of the plurality of blades is bonded to the main plate, the plurality of blades are arranged at equal intervals from each other in a circumferential direction;a shroud, having an annular shape with an opening at a center thereof, to be bonded to another respective end of the plurality of blades, with an opening at a center, the shroud to face the main plate;a bell mouth, inside the shroud and spaced apart from the shroud to allow air flow, having an inner diameter that gradually increases toward an upstream side of the air flow; andan annular member arrangeable at an outer circumferential portion of the bell mouth with a gap from an inlet portion at the gap between the shroud and the bell mouth on an upstream side of the shroud along a rotation axis direction of the shroud, anda communication flow path, to allow flow of air along the rotation axis direction of the shroud, is formed between the annular member and the bell mouth.

11. The air conditioner of claim 10, wherein the communication flow path has an enlarged portion having a cross-sectional area that gradually increases from an inlet side toward an outlet side.

12. The air conditioner of claim 11, wherein the communication flow path has, on the inlet side of the enlarged portion, a reduced portion having a flow path cross-sectional area that gradually decreases.

13. The air conditioner of claim 10, wherein the communication flow path is formed between the annular member and an outer circumferential surface of the bell mouth.

14. The air conditioner of claim 10, wherein a width of the communication flow path is less than a gap formed between the shroud and the bell mouth such that a recirculating flow passes through the gap.

15. The air conditioner of claim 10, wherein the communication flow path has, on an inlet side of an enlarged portion, an enlarged portion having a cross-sectional area that gradually increases from an inlet side toward an outlet side, and a reduced portion having a flow path cross-sectional area that gradually decreases.